1.) Field of the Invention
This invention relates to muntin grids for transparencies and to transparencies having muntin grids, and more particularly, to a grid simulating muntins having shaped ends to engage spacer frame between glass sheets of a multi-sheet unit to mount the grid within the spacer frame and between the glass sheets.
2.) Discussion of the Available Technology
Clips usually referred to as “muntin clips” are used to mount grids simulating muntins between adjacent sheets of a multi-sheet insulating unit, for example, as discussed in U.S. Pat. Nos. 5,313,761 and 6,115,989; United States Patent Publication Numbers US2004/0123557 and US2005/0028458A1 and in U.S. patent application Ser. No. 11/847,574 filed Aug. 30, 2007 in the names of Barent Rosskamp, Michael Buchanan, Stephen Crandell, William Davis and Cory Steffek and titled Retainer Clip for Grid Simulating Muntins (hereinafter also referred to as “U.S. patent application Ser. No. 11/847,574”). In general, but not limiting to the discussion, a multi-sheet insulating unit includes a glass sheet secured to each side of a spacer frame by a moisture and gas impervious adhesive-sealant to provide a sealed compartment between the sheets. The sealed compartment is usually filled with an insulating gas. The spacer frame in one embodiment of a multi-sheet insulating unit has a U-shaped cross section, e.g. as disclosed in U.S. Pat. No. 5,655,282. One of the features of the spacer frame having a U-shaped cross section is that the upright legs of the spacer frame are free to move toward and away from one another in unison with the glass sheets as the insulating gas in the compartment between the sheets expands and contracts due to pressure changes acting on the outer surfaces of the sheets.
The current practices of mounting a grid simulating muntins within the spacer frame, includes mounting the muntin clips on the ends of the grid, and mounting the clips on the interior surface of the spacer frame, or mounting the muntin clips on the interior surface of the spacer frame followed by mounting the ends of the grid on the muntin clips. United States Patent Application Publication Number US 2004/0123557 discloses a number of muntin clip designs. Although the present design of the muntin clips is acceptable for mounting grids simulating muntins between sheets of insulating units, there are drawbacks and/or limitations.
More particularly, many of the present muntin clips designs include a rigid base that bridges the two upright legs of the spacer frame maintaining the upright legs in a fixed relationship to one another. The drawback with this muntin clip design is that the muntin clip prevents portions of the upright legs and marginal edges of the sheets from moving toward one another as the pressure acting on the outside surface of the sheets increases. Another drawback with muntin clips having a rigid base is that during the pressing of the marginal edges of the sheets toward the outer surfaces of the space frame to flow the adhesive-sealant between the sheets and the spacer frame, the upright legs between adjacent muntin clips are flexible and move toward one another whereas the muntin clip is not flexible and prevents the upright legs at the position of the muntin clip from moving toward one another. The undesirable result is that the adhesive-sealant between adjacent muntin clips is thicker than the thickness of the adhesive-sealant at the position of the muntin clips. This drawback results in a “moisture sealant path” or “diffusion path” having a non-uniform thickness and can result in premature failure of the seal by allowing atmospheric air to diffuse into the sealed compartment. For a detailed discussion of the “diffusion path,” reference can be made to column 13, lines 7-43 of U.S. Pat. No. 5,655,282 which patent is hereby incorporated by reference.
Another limitation with having the base of the muntin clip supported on and spanning the upright legs of the spacer frame is that the muntin clip is in the sight line of the insulating unit. Therefore, care has to be taken to make certain that the ends of the grid simulating muntins is flush with the base to avoid any space, or minimize the space, between the ends of the grid and the base of the muntin clip. Noticeable separations between the base of the clip and the end of the grid are aesthetically unacceptable.
U.S. patent application Ser. No. 11/847,574 discloses a muntin clip that eliminates the above drawbacks. More particularly, the muntin clip of U.S. patent application Ser. No. 11/847,574 has a spacer-engaging member having bendable walls that are positioned between the upright legs of the spacer frame with the end of the grid simulating muntins below the sight line of the unit. Although the muntin clip of U.S. patent application Ser. No. 11/847,574 eliminates the above discussed drawbacks, the muntin clips of U.S. patent application Ser. No. 11/847,574 have limitations. More particularly, muntin clips are required to secure the grid within the spacer frame. As is appreciated by those skilled in the art, the open ends of the horizontal and vertical members of the grids simulating muntins have different dimensions requiring an inventory of different size muntin clips for the different size end openings of the horizontal and vertical members.
As is appreciated by those skilled in the art, it would be advantages to provide a grid simulating muntins that does not require the use of muntin clips and provides the benefits of the muntin clips of U.S. patent application Ser. No. 11/847,574. Further as will be appreciated by those skilled in the art and as discussed in the Description of the Invention, the technology disclosed in the following patents can be used in the practice of the invention: U.S. Pat. Nos. 4,873,206; 4,792,536; 5,030,593; 5,240,886; 4,170,460; 4,239,816; 4,462,884; 4,610,711; 4,692,389; 4,719,127; 4,806,220; 4,853,256; 4,898,789; 5,873,203; 6,027,766; 6,027,766; 5,177,916; 5,655,282, and 5,531,047, and U.S. Published Patent Application No. U.S. 2005/0028458. Still further, the technology disclosed in co-pending U.S. Patent Application Ser. No. 11/696377 filed Apr. 4, 2007 can be used in the practice of the invention.